Using a stair horizontal-vertical illusion to increase foot clearance over an inconsistently taller stair-riser

Abstract

Introduction Stair falls can be caused by inconsistent stair dimensions. During ascent, inconsistently taller stair risers lead to reduced foot clearances as the inconsistency goes unnoticed. A stair horizontal-vertical illusion increases perceived riser heights and foot clearance and could offset reduced foot clearances over inconsistently taller risers, though this might impact other stair safety measures. Method Twelve participants (age: 22 (3) years) ascended a seven-step staircase under three conditions: i) all steps consistent in riser height (consistent), ii) a 1cm increase in step 5 riser height (inconsistent) and iii) a 1cm increase in step 5 riser height, superimposed with a stair horizontal-vertical illusion (illusion). Vertical foot clearance, foot overhang, and margins of stability were assessed over step 4, 5 and 6. Perceived riser height due to the illusion was determined through a computer perception test. A One-Way Repeated Measures ANOVA compared biomechanical variables between conditions. A One Sample t test compared perceived riser height to the true height. Results Over the inconsistent step 5, foot clearance reduced by 0.8cm compared to consistent. Illusion increased foot clearance by 1.1cm and decreased foot overhang by 4% compared to inconsistent. On step 4 the illusion led to more anterior instability compared to inconsistent. Illusion and inconsistent led to more mediolateral stability compared to consistent. The illusion increased perceived riser height by 12%. Discussion Foot clearance reductions over inconsistently taller risers can be offset by a stair horizontal-vertical illusion. Additional benefits included a safer foot overhang and unaffected stability over the inconsistent riser. Changes to step 4 stability might have resulted from leaning forward to look at the step 5 illusion. The stair horizontal-vertical illusion could be a practical solution for inconsistently taller stair risers, where a rebuild is usually the only solution.

The effect of visual sensory interference during multitask obstacle crossing in younger and older adults

“…The older adults appear to maintain their ability to quickly detect light cue onset while walking despite age-related changes. This observation supports the use of visual cues to highlight hazards in the built environment (e.g., [ 54 – 58 ]), as our results indicate that these cues can be detected and acted on with similar latencies for younger and older adults. We note that a recent review reported that age-related differences in locomotor multitasks were most likely to be observed when the concurrent task had a visual component (see review in [ 59 ]), but the tasks included in the review typically included identification of a letter (with 26 options), rather than light cue onset.…”

“…New crosswalk signals where the entire vertical post lights up and/or crossing signals embedded in the crosswalk will reduce gaze diversion during road crossing. These approaches would supplement other environmental modifications, such as adding the horizontal-vertical illusion or tread edge highlighters on stairs, that have been shown to increase toe clearance and reduce the risk of trips and falls [ 54 – 58 ].…”

Accuracy and Precision of a Novel Photogate System to Measure Toe Clearance on Stairs

“…Whilst the toe clearance errors with IMUs appear low, their application for real-world stair assessment may be limited through needing to secure instrumentation to the stair walker (which may become obtrusive and affect natural stair walking). Additionally, errors of 45 mm associated with 2D cameras may be too large to detect very low toe clearances or meaningful differences in the presence of stair modifications [12,13].…”